A recombinant gene encoding a target protein is introduced into a host such as E. coli, a yeast or a cell, whereby a recombinant protein can be expressed. As to the expressed recombinant protein, a high purity is necessary for analyzing a function and a structure, and utilizing as a preparation or the like. For the purification of the protein, various chromatographies and the like are generally used. As a method for purifying a recombinant protein, an ion-exchange chromatography is described in Mayank Saraswat , et. al. Review Article: Preparative Purification of Recombinant Proteins. Vol 2013:18, 2013.